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Add group.h ge/gej equality functions

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This commit is contained in:
Pieter Wuille 2023-12-01 10:25:57 -05:00
parent 10e6d29b60
commit a47cd97d51
3 changed files with 38 additions and 20 deletions
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6
src/group.h
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@ -102,6 +102,9 @@ static void secp256k1_ge_set_all_gej_var(secp256k1_ge *r, const secp256k1_gej *a
*/
static void secp256k1_ge_table_set_globalz(size_t len, secp256k1_ge *a, const secp256k1_fe *zr);
/** Check two group elements (affine) for equality in variable time. */
static int secp256k1_ge_eq_var(const secp256k1_ge *a, const secp256k1_ge *b);
/** Set a group element (affine) equal to the point at infinity. */
static void secp256k1_ge_set_infinity(secp256k1_ge *r);
@ -114,6 +117,9 @@ static void secp256k1_gej_set_ge(secp256k1_gej *r, const secp256k1_ge *a);
/** Check two group elements (jacobian) for equality in variable time. */
static int secp256k1_gej_eq_var(const secp256k1_gej *a, const secp256k1_gej *b);
/** Check two group elements (jacobian and affine) for equality in variable time. */
static int secp256k1_gej_eq_ge_var(const secp256k1_gej *a, const secp256k1_ge *b);
/** Compare the X coordinate of a group element (jacobian).
* The magnitude of the group element's X coordinate must not exceed 31. */
static int secp256k1_gej_eq_x_var(const secp256k1_fe *x, const secp256k1_gej *a);

29
src/group_impl.h
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@ -354,6 +354,35 @@ static int secp256k1_gej_eq_var(const secp256k1_gej *a, const secp256k1_gej *b)
return secp256k1_gej_is_infinity(&tmp);
}
static int secp256k1_gej_eq_ge_var(const secp256k1_gej *a, const secp256k1_ge *b) {
secp256k1_gej tmp;
SECP256K1_GEJ_VERIFY(a);
SECP256K1_GE_VERIFY(b);
secp256k1_gej_neg(&tmp, a);
secp256k1_gej_add_ge_var(&tmp, &tmp, b, NULL);
return secp256k1_gej_is_infinity(&tmp);
}
static int secp256k1_ge_eq_var(const secp256k1_ge *a, const secp256k1_ge *b) {
secp256k1_fe tmp;
SECP256K1_GE_VERIFY(a);
SECP256K1_GE_VERIFY(b);
if (a->infinity != b->infinity) return 0;
if (a->infinity) return 1;
tmp = a->x;
secp256k1_fe_normalize_weak(&tmp);
if (!secp256k1_fe_equal(&tmp, &b->x)) return 0;
tmp = a->y;
secp256k1_fe_normalize_weak(&tmp);
if (!secp256k1_fe_equal(&tmp, &b->y)) return 0;
return 1;
}
static int secp256k1_gej_eq_x_var(const secp256k1_fe *x, const secp256k1_gej *a) {
secp256k1_fe r;
SECP256K1_FE_VERIFY(x);

23
src/testutil.h
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@ -7,6 +7,7 @@
#define SECP256K1_TESTUTIL_H
#include "field.h"
#include "group.h"
#include "testrand.h"
#include "util.h"
@ -27,29 +28,11 @@ static void random_fe_non_zero(secp256k1_fe *nz) {
}
static void ge_equals_ge(const secp256k1_ge *a, const secp256k1_ge *b) {
CHECK(a->infinity == b->infinity);
if (a->infinity) {
return;
}
CHECK(secp256k1_fe_equal(&a->x, &b->x));
CHECK(secp256k1_fe_equal(&a->y, &b->y));
CHECK(secp256k1_ge_eq_var(a, b));
}
static void ge_equals_gej(const secp256k1_ge *a, const secp256k1_gej *b) {
secp256k1_fe z2s;
secp256k1_fe u1, u2, s1, s2;
CHECK(a->infinity == b->infinity);
if (a->infinity) {
return;
}
/* Check a.x * b.z^2 == b.x && a.y * b.z^3 == b.y, to avoid inverses. */
secp256k1_fe_sqr(&z2s, &b->z);
secp256k1_fe_mul(&u1, &a->x, &z2s);
u2 = b->x;
secp256k1_fe_mul(&s1, &a->y, &z2s); secp256k1_fe_mul(&s1, &s1, &b->z);
s2 = b->y;
CHECK(secp256k1_fe_equal(&u1, &u2));
CHECK(secp256k1_fe_equal(&s1, &s2));
CHECK(secp256k1_gej_eq_ge_var(b, a));
}
#endif /* SECP256K1_TESTUTIL_H */